1. Field of the Invention
The present invention relates to a sample and hold circuit and a related data signal detecting method utilizing the sample and hold circuit, and particularly relates to a sample and hold circuit for detecting height of an eye diagram and a related data signal detecting method utilizing said sample and hold circuit.
2. Description of the Prior Art
Normally, an eye diagram is used to indicate the quality of a signal. Therefore, the width and height of an eye diagram are important parameters for the signal. FIG. 1A is a circuit diagram illustrating a prior art eye diagram measuring circuit 100. As shown in FIG. 1A, the eye diagram measuring circuit 100 operates at high speed and needs high speed elements, i.e. the comparator, phase interpolator and D flip-flops. The cost of the eye diagram measuring circuit 100 is high and the yield is low since it has high speed elements.
FIG. 1B is a circuit diagram illustrating a prior art sample and hold circuit 110. As shown in FIG. 1B, the sample and hold circuit includes a switching module 101, two capacitors 103, 104 and a comparator 105. The switching module 101 is used for sampling the data signal according to the turning on or turning off of said switching module 101. The capacitors 103, 104 are used for storing the sampled value, and the comparator 105 is used for comparing the sampled value and a reference voltage. However, since the bandwidth of the sample and hold circuit 100 and the speed of the comparator 105 are limited, the sampled value may be different from the actual data signal, and some error of the sampling value may occur accordingly.